I'M EXTKHN.M, SHELL. 



introducing water into it; hut. the narrow calcareous covering 

 which partially confines this tube, preventing dilatation, milit! 



strongly against this hypothesis. I TOrln^-ny's uuess seems more 

 ivasonahle. that this tuhc may not only serve as an attachment, 

 hut tlut it may also assist in the formation of a new septum, hy 

 keeping lilltMl with compressed air the vacant spare, in the rear of 

 the animal, which is to he divided oil'. Prof. Keferstein. of (Jot- 

 tiu^en. supposes, also, that the Nctutilti* /'oiii/n'/inx. in order to 

 raise itself in its shell to the place where it designs constructing 

 a new partition, employs the tension of an aeriform fluid, which 

 it produces from the hot.tom of its sack, and which presses its 

 hody upward. The ail 1 disen^a^ed hy the Nautilus develops a 

 eonsiderahle force, hecause it conquers not only the resistance of 

 weight of the animal itself, hut also that of the weight of ahout 

 six atmospheres, which presses upon it ill its hahitual station at 

 the hottom of the sea. 



In the Report of the Brit. Assoc. for l<si;4, Harry Seely says: 

 "On examining a Nautili tt-xlwU, two la rv muscles are seen to 

 have heen placed in the lower part of the body-chamber, :md 

 connecteil i-oiind the involute spire hy a narrow muscle an 

 arrangement to which the shell may owe its involute form. IJe- 

 neath the muscles are the liver, which overlaps the spire, the 

 ovaries, which ahut on a lar^e [.ai't of the septum, and certain 

 digestive organs ahove these. IJcfore any new chamhei- can he 

 made, the shell-muscles must have moved forward: and he lore 

 any increase in the, ovaries can take place, a place must he formed 

 hehind. As the animal steadily liTows, all its organs would 

 culture: and, with each successive hrood. the disten<led ovaries 

 would require more sjniee. There is a similar gradual increase 

 in the >i/e of the aii'-chamhei's. and. since the development of ova 

 would necessitate a forward u'l'owt h of t he mollusk. t he discharge 

 of the ovaries would leave an empty space hehind. into which the 

 animal could not ret ire. which would then he shut oil' hy a sep- 

 tum moulded on the animal's hody. In the male Nuulilu.^ 1 he 

 testcs are placed in exactly the same posit. ion as the ovarie- of 

 the female, and, except ing the liver, form the largest orpin in the 

 hody. It may therefore IK- concluded, that, the development of 

 the male organs would produce results similar to those in the 

 other M'X ; and Likewise end in the formation of chamhei's. 



